Production of nitriles



Patented Oct. 6, 1942 NT OFFICE 'PRonUcrIoNoF NITItILES Albert E. Rainsi'ord, New York, and John H. p V I Pearson, Flushing, N. Y., assignors to General 7 Chemical Company, New York, N. Y., a corporation of New York Serial No. 321,406

' No Drawing. Application February 29, 1 940,

-14 Claims. (01. 260-464),

This invention relates to a process for production of nitriles and the corresponding acids.

Organic acids have been prepared heretofore by hydrolysis of their nitriles. It has been proposed toprepare nitriles, e. g. the nitriles of aliphatic acids, by reaction of alkyl sulfates and potassium cyanide in aqueous solution. For ex ample, propionitrile has been prepared from diethyl sulfate and an aqueous solution of potassium cyanide; When attempts have been made to substitute the less expensive cyanides, e. g. so-

dium cyanide, for the potassium cyanide in this reaction yields have been very poor, due to hydrolysis and decomposition of the reactants. In

order to utilize sodium cyanide rather than potassium cyanide it has also been proposed to produce propionitrile by heating a dry mix Of sodium ethyl sulfate and sodium cyanide. this process the yield is also very low, due to decomposition of th reactants. V

It is an object of this invention to provide an improved process for preparing 'nitriles involving the use of metal cyanides as reactants, in'which process the less expensive cyanides such assodium cyanide may advantageously-be used and high yields obtained. I I

We have discovered that high yields of anitrile may be obtained b reacting a metal cyanide with a sulfuric or phosphoric 'acid ester in a nonaqueous, high boiling liquid medium; for example,

by mixing the reactants with a non-aqueous liquid boiling above about 130 C. and inert with respect to the reactants and products, and heat-.

ing the mixture. A nitrile thus produced may be hydrolyzed to form the acid, and esters or other derivatives may be propared from the acid.

When a metal cyanide is caused to react with a sulfuric or phosphoric acid ester, the products of reaction are a metal sulfate or phosphate and an organic cyanide; for example, sodium cyanide and diethyl sulfate may be reacted to form, sodium ethyl sulfate and ethyl cyanide. The organic cyanidethusformed is a nitrile of a carboxylic acid; e'. g. ethyl cyanide is the nitrile of propionic acid. Accordingly, the organic cyanide may be hydrolyzed to form the corresponding acid; for example, ethyl cyanide (propionitrile) may be'hydrolyzed to propionic acid by heating with an aqueous sulfuric acid solution.

For the reaction between a metal cyanide and a sulfuric or phosphoric acid ester in the absence of water, in accordance with our invention, cyanides such the alkali metal and alkaline earth metal cyanides, and cyanides of heavy metals such as copper and zinc may be employed; alkali 55 However; in

metal and alkaline earth metal cyanides are preferred. Our' process makes possiblethe eflicient use of inexpensive metal cyanides in the production of nitriles, the use of sodium cyanide being particularlyfiadvantageous because of its availability and low costs For example, bythe process of our invention a 90% yield of the nitrile may be obtained with the inexpensive sodium salt; in reacting sodium cyanide and a sulfuric acid ester in an aqueous medium we have found the yield of nitrile product is not above 61%. The process of our invention,"therefore, has the important advantage. of making possibl the use of cheap sodium cyanide to produce a very high yield of V nitrile, and the corresponding organic acid and derivatives thereof may accordingly beeificiently produced from sulfuric or phosphoric acid esters by first preparing the nitrile in accordance with our invention.

Esters suitable for the process of our invention may be obtained by reacting sulfuric or phos-' phoric acid with the corresponding alcohols, by

treating olefin hydrocarbons with sulphuric or For ex phosphoric acid, or by other methods. ample, ethylene or other olefins may be reacted with sulfuric acid to form sulfuric acid esters by addition of sulfuric acid to the double bond of the unsaturated hydrocarbon. Ethylene and sulg furic acid, for instance, may be reacted to form diethyl sulfate, propylen and sulfuric acid may be reacted to form di-isopropyl sulfate, and in general the lower olefins may be reacted with sulparticularly suitable furic acid to form the dialkyl sulfates which are for the process of our invention.

The non-aqueous, high boiling liquid medium,

in which thereaction'is carried out may be any liquid which is inert with respe-ct'to both the reactants and the products of reaction and which has a boiling point about about 130 C. A number of organic liquids are suitable for thisv purpose; for example, "decahydronaphthalene, tetra- H 'hydronaphthalene, xylene, alcohols of high molecular weight, pine oil and chlorinated com- 7 pounds such as dichlorodiethyl ether. It'is preferable to choose a liquid reaction medium which has a boiling point substantially above the boiling point of thenitrile product. We have found decahydronaphthalene, tetrahydronaphthalene and xyle ne, particularly decahydronaphthalene, to be' advantageous as non-aqueous reaction media for the production of the lower boiling nitriles such as propionitrile in accordance with the process of our invention. The above-described high boiling non-aqueous liquid, we have 2 found, prevents hydrolysis of the ester and inhibits decomposition of the cyanide, thereby increasingthe yield of nitrile. The use of a nonaqueous, highboiling liquid reaction medium, accordingly, is an important feature of our invention.

In practicing our invention the liquid reaction medium, metal cyanide and ester are mixed, whereupon the ester and cyanide react to form a nitrile; the nitrile product is then separated from the reaction mixture, for example by distillation, the vapors being fractionated, if necessary, to separate the nitrile product from other constituents of the reaction mixture (e. g.,. liquid reaction medium) which may volatilize. v Wicon sider it preferable, however, to employ a liquid reaction medium having a boiling point sufii-,

ciently above that of the nitrile to make such fractionation unnecessary.

In the practice of our invention we have found it particularly advantageous to suspend the metal cyanide in the liquid reaction medium, heat the mixture to a temperature substantially above the boiling point of the nitrile product (e. 8., about 30 to 60 above the nitrile boiling point) and slowly add the nitrile and propionic acid, the butyronitriles and butyric acids, and the valeronitr iles and valeric acids. The production of the lower saturated aliphatic acids and their nitriles is advantageous industrially, in that petroleum cracking still gases constitute a convenient source of lower olefin hydrocarbons from which the lower alkyl sulfates or phosphates, mayreadilylbej'prepared by reaction of the olefins with sulfuric or phosphoric acid. For example, some cracking gases have been found to contain about ethylene, 12% propylene and 6% isobutylene. These unsaturated hydrocarbons may, for example, be reacted with sulfurie acidto form sulfuric acid esters,

e. g. diethyl sulfate, di-isopropyl sulfate and ditertiarybutyl sulfate, respectively, and the sulfates thereafter reacted with sodium cyanide in accordance with the process of the invention to form the nitrile of the saturated aliphatic acid '25 ester to the reaction mixture at such a rate that the reaction temperature is maintained in the desired range. For example; in a preferred method of carrying out the process of our invention sodium cyanide is suspended in a liquid such as decahydronaphthalene, the slurry is heated to a temperature about 30 to 60". above the boiling point ofthe'nitrile product and rapidly agitated while the ester is gradually added thereto at such a rate that the reaction 06111 perature is maintained in the above indicated range. In the production of propionitrile, for exmaintained in the range about 130 to 160 C.

We have found the production of nitriles may be carried out with unusually high efilciency when ample, the reaction temperature is preferably the reaction temperature is maintained ashere indicated and accordingly maintenance of reactiontemperature as described'above and control of esteraddition for that purpose are further important features of our invention.

The crude nitrile obtained as above-described maybe purified by rectification or may be hydrolyzed without purification directly to the correspondin acid formed during the reaction. The organic 7 acid. The hydrolysis of the nitrile to I the acid may be accomplished by heating in an by hydrolysis and other derivatives prepared therefrom as described above.

The followingexample the'rea'ction is highly exothermic the dropwiseaddition of diethyl sulfate maintained the reaction temperature in the desired range. Upon completion of the-reaction about 5'7 parts of crude ethyl cyanide parts of whichboiledin the range of 96 to 98 0., representing a 90% yield of ethyl cyanide based upon the weight of sodium cyanide charged.

55 parts of crude ethyl cyanlde obtained by the' above process were mixed with 196 parts of 98% sulfuric acid and '12 parts of water. The mixture was .refluxed with stirring for 3 hours.

.The aqueous reaction mixture was thereafter extracted with ether to obtain propionic acid;

. the'ether solution of propionic acid was dried acid thus produced may be used to manufacture salts, esters or other derivatives; 'forexample,

from propionic acid there may be prepared propionates, cellulose derivatives. etc., or, the acid or its esters may be used in preparing artificial fruit flavors and perfumes.

The process of our invention, asaboveindicated, is applicable in general to the production of nitriles and corresponding carboxylic acids and other derivatives from sulfuric or phosphoric acid esters. The production of the lower saturated aliphaticacidsand their nitriles, especially propionitrile and propionic acid, is of particular importance; as examples of. such nitriles and acids there may be mentioned, in addition to propioand distilledto separate the ether from the acid. A yield of propionic acid of boiling range to C. (based on the ethyl cyanide) was obtained. V

Similarly, sodium cyanide and triethyl phosphate may be. reacted in decahydronaphthalene to form ethylcyanide, which may then be hydrolyzed to form propionic acid as described above.

Where reference is madein the specification and claims to ethyl, propyl,'butyl or alkyl esters ,(i. e. sulfates or phosphates), theterm is intended to be used in its usual general sense, i. e. to include boththe mono and poly alkyl esters,

and the salts of the acid esters, and to include j all isomers of the alkyl group. 7

Since certainv changes may be made in the processes above described without departing from illustrates the process of our invention. All quantities are in parts by weight.

had been obtained as distillate, 49

the scope of the present invention, it is intended the description shall be interpreted as illustrative and not in a limiting sense. I

What is claimed is:

1. A process which comprises reacting an ester from the group consisting of sulfuric acid and phosphoric acid esters with a metal cyanide in a non-aqueous liquid medium having a boiling point above 130 C. to form a nitrile. 2. A process which comprises reacting an alkyl sulfate with a metal cyanide in a liquid medium having a boiling point above 130 C. ,to form a nitrile, the reaction being carried out in the substantial absence of water. V

3. A process which comprises reacting an alkyl phosphate with a metal cyanide in a liquid medium having a boiling point above 130 C. to form a nitrile, the reaction being carried out in the substantial absence of water.

4. In a process for production of a nitrile by reacting an ester from the group consisting of sulfuric acid and phosphoric acid esters with a metal cyanide, the improvement which comprises carrying out said reaction in a non-aqueous liquid medium-having a boiling point above the boiling point of the nitrile and above 130 C.

5. A process which comprises reacting an ethyl ester'from the group consisting of sulfuric acid and phosphoric acid esterswith a metal cyanide in a non-aqueous liquid medium having a boiling anides in a non-aqueous liquid. medium having a boiling point above 130 C. to form a nitrile. 9. A process which comprises reacting ethyl sulfate with a cyanide from the group alkali metal and alkaline earth metalcyanides in a non-aqueous liquid medium selected from the group decahycironaphthalene, tetrahydronaph thalene and xylene, to form a nitrile.

10. A process which comprises reacting ethyl phosphate with a cyanide from the'group'alkali metal and alkaline earth metal cyanides in a non-aqueous liquid medium selected from the group decahydronaphthalene, tetrahydronaphthalene and xylene, to form a nitrile.

11. In a process for the production of a nitrile by reacting ethyl sulfate with sodium cyanide, the improvement which comprises gradually adding the ethyl sulfate to the sodium cyanide suspended in a non-aqueous liquid medium selected 7 from the group decahydronaphthalene, tetrahydronaphthalene, and xylene, at such a rate that the reaction temperature is maintainedlwithin the range about 130 to about 160 C.

sulfuric acid and phosphoric acid esters with a metal cyanide, the improvement which comprises adding the ester to the metal cyanide suspended in a non-aqueous liquid reaction medium having a boiling point above the boiling point of the nitrile and above 130 C., at such a rate that the reaction temperature is maintained within a predetermined range above the boiling point of the nitrile.

8. A process which comprises reacting an ester from the group consisting of sulfuric acid and phosphoric acid esters with a cyanide from the group alkali metal and alkaline earth metal cy- 12. In a process for the production of a nitrile by reacting ethyl phosphate with sodium cyanide,

the improvement which comprises gradually' adding the ethyl phosphate to the sodium cyanide suspended in a non-aqueous liquid medium selected from the group decahydronaphthalene, tetrahydronaphthalene, and xylene, at such a rate that the reaction temperature is maintained within the range about to about C.

13. In a process for production of propionic acid, the steps which comprise heating an ethyl ester from the group consisting of sulfuric acid and phosphoric acid esters with sodium cyanide in a non-aqueous liquid medium comprising decahydronaphthalene to form propionitrile, and hydrolyzing the nitrile thus formed to propionic acid.

14. In a process for the production of a nitrile by reacting an ester from the group consisting of sulfuric acid and phosphoric acid esters with a metal cyanide, the improvement which comprises gradually adding the ester to the metal cyanide suspended in a non-aqueous liquid medium having a boiling point above the boiling point of the nitrile and above 130 C., at such a rate that the reaction temperature is maintained within the range about 30 to about 60 ALBERT E. RAINSFORD. J OHN- H. PEARSON. 

